How to Identify the North From South Pole on Magnets
There are several options to determine the polarity of a magnet, that is, which end is the north pole and which end is the south. The basic strategy is comparison: seeing how it behaves around another magnet. When comparing two magnets, the principle used is that like poles between two magnets repel and unlike poles attract.
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Instructions
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Tie the magnet in the center using a string and hang it so that it hangs horizontally---the two suspected poles on opposite sides of the string. With time, the magnet will rotate its north pole toward the Earth's geographic north pole. (The Earth itself is magnetic from molten currents underneath its crust.) This option works best when the magnet is rodlike and light.
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Draw it near a compass or other marked magnet. The north end of the compass needle will be drawn toward the south pole of the unmarked magnet.
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Take a coated wire with bare ends and coil it up. Touch the bare ends to the opposite ends of a battery. The coil is now an electromagnet. The electrons coming from the negative (-) end of the battery flow through the wire to the positive (+) end of the battery. Depending on which end of the coil you are looking at, the electrons will move clockwise or counterclockwise. If the coil is sitting with its axis vertical, and the electrons are passing through the coil in a clockwise direction, then the top of the coil is the north pole end. It will attract the south end of your unmarked magnet and repel the north end.
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Tips & Warnings
Note that the Earth's geographic north pole is actually near its magnetic south pole. Therefore, it attracts the north pole of magnets.
To read more about the third step, search on the words "right-hand rule" and "solenoid."
Some magnetizable material can switch polarity. Therefore, test your magnet to see if it is such a material by flipping it around and seeing if it behaves the same way to the magnet it's compared to as when it was in the opposite orientation.
